From the old dota-allstars anime forum actually and before I get started I need to take a quote from mr44mag (edited slightly):

from mr44mag
Edit: This thread is now a warning about this series. I just saw the fist episode and I'm still shaking. Its going to take years of therapy to undo this. I'm a big fan of gore and violence, especially in anime. I've seen every Freddy, Michae, and Jason Voorhees movie and just about every single horror movie made from 1995 to present day and nothing has every bothered me as bad as this has ... god I'm going to have nightmares about this. The first 15 minutes puts the Texas Chainsaw Massacre to shame

After hearing that I was intrigued enough to acquire Elfen Lied and view it myself and I was amazed.

This show is not intended for anyone with a weak heart or those that harbor an extreme dislike of animated nudity. mr44mag explained what can happen quite well and if you are worried after reading just that quote, I highly recommend you not attempt to watch this.... or atleast don't blame me if you do and it gives you heart trouble. With that said, and for those reasons, I will not be including any images from Elfen Lied in this thread or the direct wikipedia link (the article contains some graphic content). If you want outside information on this anime I will ask you to find the wikipedia article on your own or you may ask me via PM.

Genre: Horror, Drama, Supernatural, Science Fiction, Thriller, Romance, Seinen, Shounen, Psychological, Action
Episode count: 13 + 1 OVA Special

The story begins with a naked young girl (Lucy) escaping under odd circumstances from an island research-facility off the coast of Kamakura in the Kanagawa Prefecture of Japan. Lucy manages to nonchalantly dismember and slay 23 of the research-facility staff with some form of seemingly supernatural power and gets outside. A sniper is ordered to kill her but only manages to ricochet the bullet off the metal helmet encasing her head. Lucy falls off a cliff into the sea and is not found again by the research staff.

My Addition: After this incident the scenery changes drastically and the viewer will gain atleast a bit of relief after the horror they have just seen. You will be introduced to two of the other main characters quickly and the series will begin to take shape.

Opening theme: "Lilium" by Kumiko Noma.
Closing theme: "Be Your Girl" by Chieko Kawabe.

-The storyline of Elfen Lied is incredibly deep and thought provoking. I have not yet watched an anime that drove me into more thought or given me more drive to watch another episode.
-This is obviously meant for an older audience with the ability to really delve into what is happening with and between the characters.
-Emotionally charged: I can't describe how amazing the range of emotion that watching this anime can take you through.
-How the understanding of various parts of the plot will make you either hate, love, or fully comprehend the magnitude of various characters and their interactions.
-This is my absolute favorite anime and I have seen quite a bit of many different genres. Take that with a grain of salt if you will, but I needed to say it!